Monitoring system of comparator type



Jan. 3, 1950 I c. J. MERCHANT 2,493,543

MONITORING SYSTEM OF COMPARATOR TYPE Filed Sept. 8, 1947 2 Sheets-Sheet 1 AMPLIFIER EQUALIZER OSCILLATOR AMPLIFIER INVENTOR. CHARLES J. MERCHANT SOURCE RNEY c. J. MERCHANT 2,493,543 MONITORING SYSTEM OF COMPARATOR TYPE Filed Sept. 8, 1947 Jan. 3, 1950 2 Sheets-Sheet 2 AMPLIFIER AMPLIFIER AMPLIFIER SOURCE INVENTOR. CHARLES J. MERCHANT AT RNEY Patented Jan. 3, 1950 "2393543 1 I MONITORING SYS'EEM 0F COMPARATOR 1 YPE Charles 3. Merchant, olevelanii'iteights, Ohio, as-

sigmr a) The Cleveland, Ohio,

Brush Development company,

a cfirporatich bf Ohio Application September 8, 1947, Serial No. 7732, 815

This invention relates generally to mbnitoi ing systems for comparing an article or a view with a subsequent article or view and is speeim cally directed to an arrangement for aeteetingchanges. v

There are many uses for a mohitcriiig system in which an article or a View is subsequently compared with a succeeding article or view in order to determine whether any changes have taken place. Thus such arrangements are some= times used for monitoring articles or material which is being made on a production basis in order to detect changes which take place a production line. A very satisfactory burglar alarm is provided by an arrangement which coin= pares one view of a scene or room with a subse= quent view of the same scene or same room in order to determine whether any'changes have taken place in the meantime. Such an arrange= ment, for example, can be made to show th presence of an intruder; smoke, fire, etc. Such monitoring systems of the com arator type may also be useful in supervising the traffic or park= ing of airplanes along an air strip, for compar ing the signals received in one radar scan with those received during a subsequent scan ete.

Monitoring systems which have been hitherto available have not been such as to to provide an appreciable memory. A memory is newssary if a comparison of an article or scene is to be made with a subsequent article or scene. The memory or storage systems which have hitherto been used have been deficient primarily in that they have not been suitable for unattended use and. in that the systems have not been such as to provide a convenient and easy change or the record with which the comparison is made;

It is an object of the invention, therefore, t6 provide a monitoring system of the comparator type which is not subject to one or more of the above-mentioned disadvantages of prior siieh systems. I i

It is also an object of the invention to provide an improved monitoring system of the compare tor type.

It is still another object of the invention te provide a motion-indicating system which is rel atively simple and inexpensive and in which the system may be eifective to detect motion at any point within a given area or field regardless of the fact that the area or the field ma not enclosed.

In accordance with the invention a monitor:

ing system comprises, recording and reprodilm ing means, means for scanning a field to derive 4 claims. (01. 250 200) a first set'of signals varying in accordancet'vith the new scanned, and means for recording these signals on the retarding means. The arrange: ment also comprises means fer subsequently scanning this field in the same manner used in the first=inehtioned scanning t6 derive a second set of signals varyingin accordance with the field scanned, together with means fpr deriving the recorded signals from the recbrdihg means and for synchronously compa ing the last-named signals" with the abcve=inentiohed second set of s gnals. This cbh paris'onis ma e to sewer any changes in the new between the above-mentinned scahnings.

After the above sequence has taken place, the recbr'di'ng can be erased and the process re pleated, oi", if desired; the recording can be re tained for-comparison purposes until it is changed at the will of the operator; as, for example; where the articles or materials in a production line are c'iiifip'ai'd with a standard represented by the recording and where the operator changes the standard by any suitable means; used as aburglar alarm; the recordingmay be retained until changed by the operator although it is preferable to cause the resa e to change periodically in an autematic manner as described more ful y hereinafter; 1

For a better understanding bf the present invenues; together with ether and further ob ects thereef; referene' is had to the following desription taken in tonne-anon with the accompanying drawings and the scope will be pointed out in the ap ended claims.

In the drawings, Fig. 1 is an illustration of a monitoring s stem in acirdanc with the in ventio'n: Fig; 2 illustrates a fiii thei modification of the invention; and Fig; 3 is utilized to explain a p02rtion of the operation of the system of Fig.

Referring now more partiemarl to the drawings, there is illustrated in Fig.- 1 a monitoring system which comprises a recording and retro: d'ucing means; While, in general, any type of recording and reproducing can be utilized; the preferred embodiments of my invention utilize recording and reproducing means of the magnetic type, primarily for the reason that th steps of recording and reproducing are very much simpler in magnetic arrangements and ass fi the reason that; in a magnetic system, the re cording can easily be erased.- Thiis'; iii Fig; 1 the r'ecdiding and reproducing lnafis comp a di'sk l0, which may be (if brass with a plating of magnetic-material the lower face thereof;

V the light 18 is energized being driven by a motor l3 infra-red or ultra-violet light. If desired, a

source of sound signals or of may be used in scanning. However, a preferred embodiment of the invention is that illustrated in Fig. l in bodied in a device which may be a burglar alarm.

light source If! mounted for rotation upon shaft l2 and adapted, by means of a lens 19 included within a housing 20, to provide a light spot which.

also rotates with the shaft l2. If desired, masking means may be provided so that a narrow vertical ribbon of light is provided. Also mounted on the shaft I2 is a second housing 22 which in-: cludesa lens 23 for receiving reflected light from all objects upon which lens 19 projects light. A photocell 25 is included within the housing 22 in order to develop electrical signals from varia-' tions of the light picked up by lens 23.

The arrangement of Fig. 1 also includes means for recording the above-mentioned electrical signals on the recording medium which includes disk Ill. This last-named means includes a switching arrangement for connecting the electrical output of photocell 25 to the recording head H through an amplifier 21. The switching arrangement mentioned above includes a drum 28 which is driven by the motor l3 and upon which are mounted slip rings and commutator segments to provide the above-mentioned switching together with further switching which will be described subsequently. The drum 28 includes slip rings 29,

mutator segments 33, 34, 35, and 36, each slip ring and commutator segment having a'brush effective therewith as indicated by the arrows in the drawings. The signal output of photocell 25 is taken from slip rings 38, 39 on shaft l2 and from an A. C. source 40 through slip rings 4| and 42 also on the shaft l2. The A. C. source 40 is also used to drive the motor l3.

The arrangement of Fig. 1 also comprises means for subsequently scanning the above-mentioned field or view in the same manner used in the first-mentioned scanning to derive a second set of signals varying in accordance with the field scanned. This is done in the arrangement of Fig. 1 by a subsequent rotation of the shaft [2 in order to cause the'beam from source I8 to scan the same field that was scanned in the pre vious rotation of the shaft.

-.The arrangement also comprises means for deriving the signals which were previously recorded on the disk In and for synchronously which the monitoring system is em- 30, 3| and 32' and com-- ultra-sonic signals In Fig. 1, the means for scanning'comprises a switch 55. Signals in the same manner that the signals picked'up by the first scanning are distorted due to being recorded on the disk it and subsequently derived therefrom and amplified in amplifier 35.

In order to compare the signal outputs of amplifier 45 and equalizer 46, they are connected with opposite polarity to the input circuit of a vapor-filled tube it by .means of a transformer having primary windings 49, 56 and a secondary winding 5i. A bias source 52 is provided in the input circuit of tube 48 in order to maintain the tube normally non-conductive in the absence of i an input signal thereto.

. The output circuit of tube 48 includes a load resistor 53, a source of power supply 54, and a which cause the vapor-filled tube 38 to fire are effective to energize a relay 5B, the contacts of which are utilized to connect source 51 to a bell or alarm device 58.

In order to cause the bell 58 to ring in case the power supply fails or is disconnected, normally closed contacts of a relay 60, which is energized comparing these last-named signals with the set of signals derived as a result of the above-men- V "ribbon from source i8 and or field scanned.

plied to the system, ,the relay 6E3 picks up thereby from the power source 40, are connected in parallel with the normally open contacts of relay 5B which are utilized to close the bell circuit when the tube 48 fires.

In order to erase the record which has been provided on disk 62 is. provided and is adapted .to be connected to the head I 1 through slip ring 3| and commutator segment 35.

In considering the operation of the system which has just been described, it will first be assumed that the ratio of the gears l4, 15 between shaft l2 and the shaft of motor I3 is such that shaft l2 makes many revolutions, for example, revolutions, for one revolution of the motor shaft. It will further be assumed that the commutator segment 34 is only of sufiicient lengththat the coil II is energized for recording during exactly one complete revolution of the shaft [2. It will further be assumed that the commutator segment 33 is of sufficient length and is so oriented that the amplifier 45 is connected to the coil II for 48 revolutions of shaft [2 immediately following the revolution of shaft [2 during which the recording is made through commutator segment 34. It will also be assumed that the commutator segment 36 is identical with commutator segment 33 so that the equalizer 46 is connected to the output circuit of amplifier 2] during the entire interval of time that the amplifier 45 is connected to coil II for reproducing the record previously made on disk if]. It is furthermore assumed that the oscillator 62 is connected to the coil I I, through the commutator segment 65, for one complete revolution of the shaft l2 immediately following the above-mentioned 48 revolutions during which the equalizer 46 is connected to the amplifier 41 through commutator segment 36. Under the conditions stated it will be seen that; when power is supplied to the system from the A. C. source 48, the motor [3 is energized to cause the shaft [2 to'rotate to scan the room or field of view with a light beam or that reflected light from this beam or ribbon is focused by lens 23 on photocell 25, thereby to generate electrical potentials varying in accordance with the scene Also, as soon as power is supde-energizing the bell 5B. Thus under the conditions described, the bell 58 is silent because switch is open.

he wi chi i Iii, a high-frequency oscillator Pre r bly hea ed wiel s.

5 the fielder scene which is scanned by the. light from the source I8. It may, for example, be associated with the lock of the door of the building in which the arrangement of Fig. l is to be utilized as a burglar alarm. It will now be assumed that the switch 55 is closed by the last person to leave the building, for example, by the act of locking the door. Under these conditions,

it will be seen that, during one complete revolution when contact segment 34 is effective, the

room, scene, or field is scanned by the light beam and the signals developed in photocell 25 are applied to. the coil II through the amplifier 21 and the commutator segment 34. This causes a recording to be effected on a magnetic material of disk Ill during this complete revolution of shaft I 2. Immediately after this revolution of shaft I2 and for the next 48 revolutions of shaft I2, the output signals of the photocell 25 are connected through amplifier 21, commutator segment 36 and equalizer 46 to the winding 50 in the input circuit of tube 48. Also, during this same interval of time, the winding II, which picks up the signals which have previously been recorded on disk I8, is connected to the winding 49 in the input circuit of tube 48 through contactor segment 33 and amplifier 45. If there is no change in the view or scene which was scanned originally by the beam I9 and which is again scanned during the above mentioned 48 revolutions of shaft I2, equal and opposite signals appear in windings 49 and 50 and no signals are applied to the input circuit of the tube 48. However, any change in the field scanned during the 48 revolutions of shaft I2, as distinguished from the field scanned during the first revolution of shaft I2, results in an input signal to tube 48 which causes the tube to fire.

Transformer 49, 58 and 5| is preferably of the peaking type so that a positive signal pulse is always derived from any pulse signal which is effectively applied thereto regardless of whether or not this pulse signal is positive or negative. When the tube 48. fires, the relay 56 is energized causing the bell 58 to sound an alarm. Assuming, however, that the above-mentioned 48 revolutions take place without causing tube 48 to be energized, the oscillator 62 is connected to the coil II during the next complete revolution of shaft I2 through the commutator segment 35, thereby to erase the entire recording on disk III. After this sequence of events, the cycle is again repeated continuously so that, at any time a change takes place in the field scanned by the light beam I8, the alarm 58 is energized. In a preferred embodiment of the invention the shaft I2 is caused to rotate at a speed of one revolution per second.

The arrangement of Fig. 2 is generally similar to'that of Fig. 1 and similar circuit elements have identical reference numerals, while analogous circuit elements have identical reference numerals primed. The circuit of Fig. 2 differs from Fig. 1, however, in that two recording disks Ill and I are provided on the shaft I 2. Also, in Fig. 2 the ratio of gears M, I5 is such that the shaft I2 makes two revolutions for each revolution of motor l4. The drum 28' in Fig. 2 differs from drum 28 in Fig. 1 in that commutator segments 65 and 66, connected respectively to slip rings 81 and 68, are each contacted by their cooperating brushes during one-half revolution of drum 28. similarly, contact segments 69 and I0 are contacted during the succeeding half revolution of drum 28'.

In: the arrangement of Fig. 2 separate erasing, recording and reproducing coils are provided for disks I8 and I 0. Thus the disk I 0 comprises a recording coil I2, an erasing coil 13 and a reproducing coil 14, while the disk I0 comprises a recording coil 75, an erase coil I6, and a reproducing coil TI. The reproducing coils l4 and 11 are connected, respectively, to windings 49 and 50 of the input transformer of tube 48 through amplifiers 45 and 45". The recording coils I2 and 15, respectively, are connected to the brushes which contact commutator segments 69 and 65, respectively. The erase coils 13 and 16 are connected, respectively, to the brushes which contact commutator segment 10 and commutator segment 66. The angular disposition of the recording coil, the erase coil and the reproducing coil of disk II) are illustrated in Fig. 3 by the correspondingly numbered dots which indicate relative position The coils cooperating with disk I0 are similarly located around disk III.

In considering the operation of the arrangement just described, it will be assumed that power has been supplied to the system to cause relay 60 to de-energize the bell 58 and that the switch 55 has been closed by locking a door in which the system is includedas a burglar alarm. It will be seen that, during a complete revolution of the disk III, for example, the erasing coil I3 and the recording coil 12 are connected, through contact segments I8 and 69, respectively, to'the oscillator 62 and to the output circuit of amplifier 27, respectively. Under these conditions, and assuming a clockwise rotation of the disk I0 as indicated in Fig. 3, all recordings which have previously been made on the disk III are erased due to the energization of winding 13 from the oscillator 62, but'immediately thereafter a new recording is placed upon the disk In due to the fact that the recording coil I2 is connected to the photocell'25 through the amplifier 27, slip ring 61, and commutator segment 69.

It will also be seen that, during the next complete revolution of shaft I 2, the coils I2 and I3 are deenergized and the previous recording remains on disk I0. However, during this next revolution of shaft I2, recording coil I5 is connected to the photocell 25 through the amplifier 21, slip ring 61 and commutator segment 65 while the erase coil 16 is connected to the oscillator 62 through the commutator segment 66 and the slip ring 68. For the third revolution of shaft I 2, the coils l2 and 13 are again energized, as described in connection with the first revolution of shaft I2, while during the fourth revolution of shaft I2 the coils 15 and 16 are energized, as described in connection with the second revolution of shaft I2. This process repeats indefinitely.

Under the conditions described there are always present on the disks I0 and III, at the positions of the reproducing coils I4 and TI, respectively, a recorded signal. This recorded signal on one of the disks corresponds to the current revolution of the shaft I2, while the record on the other of the disks corresponds to the preceding revolution of shaft I 2. Thus, the differential input to winding 5| always provides a synchronous comparison of the scanning of one field by light I8 with the scanning of the previous field by light I8. Any change in these succeeding fields causes relay 48 to be energized and the alarm 58 to be actuated in the manner described in detail in connection with the description of 7 Fig. 1. ,7 This description. will not be repeated here. Inthe arrangement of Fig. 1 it will be seen that, during one scanning cycle, a record is made which, is thereafter comparedwith the signals picked up during the next 48 scanning cycles. Such an arrangement, therefore, is effective to provide an arrangement in whichvery minutev orslow changes in the field being scanned. are detected. In the arrangement of Fig. 2, onthe other hand, the system is such that the signals derived during the scanning of one field are always compared with the signalsderived during the preceding scanning of the field. The system ofsFig. 2 is thus efiective to detect radicalchanges which take place between the scannings. However, it will be understood'that various combi-. nations of these twov systems can easily be ef-.

'fected by changing the gear ratios involved in thedrive between the shaft of motor I4 and the shaft [2 and by changing the switching pro-' vided by the commutator segments of the'motordriven commutator. It will also be understood: that the principles of both systems can be used simultaneously to detect fast and slow changes.

It will be understood that, in some cases, the light source l8 can be omitted and a non-directional source 'of radiant energy used instead. Sunlight maybe used as the source of radiant energy, if desired.

While there have been described what are at present considered to be the preferred embodiments of. this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. A monitoring system comprising: recording and reproducing means; means for scanning a;

. the same manner-used in said first-mentioned scanning to derive a second set of signals varying in accordance with the field scanned; means for recording said second set of signals on said recording means; and means for reproducing said recorded signals and for synchronouslycomparing the reproduced signals corresponding 'to said first-mentioned scanning and said reproduced signals correspondingto said subsequent scanning, thereby to detect an changes in said field between said scannings. I I

2. -A monitoring system as set forth .in claim 1, further characterized'by said means for scanning a field including a light source for providing a light beam of restricted area.

3. A monitoring system as set forth in claim 1, further characterized by said means for scanning a field including a source of radiant energy and a receiver of reflected radiant energy spacedaway from said source of radiant energy.

4. A monitoring system as set forth in claim 1, further characterized by said means for scanning a field including a light source for providing a light beam of restricted area and a photoelectric cell receiver of reflected light spaced away from said light source. CHARLES J. MERCHANT REFERENCES CITED The following references are of record in the.

file of this patent:

UNITED STATES PATENTS Bliss Nov. 19, 1946' 

